@Aashish_AS Thank you for providing the tool. However, even this tool could not restore. Is the restoration method a little different for RE450? Can you see if there are other ways to restore it?

@terziyski Thank you for providing good information. However, unfortunately I saw tftp, but there was no communication log from the router. I don't want to give up yet. Would you please join us in...

(I chose AC1750(RE450) because it does not exist in the model name.) I tried to put OpenWrt in AC1750(RE450). However, the flash failed and I got into a boot loop. I can't connect to a computer. I...